Digital television services have been provided within certain geographical areas using direct broadcast satellite (DBS) systems, which also may be referred to as direct-to-home (DTH) systems. A DBS system may include at least one geostationary orbit (GSO) satellite or non-GSO (NGSO) satellite. A DBS satellite receives television content over uplinks from one or more terrestrially-based hubs, and broadcasts the content on downlinks toward populations of user equipment systems.
A first type of DBS system includes at least one GSO satellite. A GSO satellite has a geocentric orbit directly above the equator, and this orbit has the same orbital period as the sidereal rotation period of the Earth. Accordingly, a GSO satellite appears to be substantially stationary with respect to a point on the surface of the Earth, and a GSO satellite may provide services within a fixed geographical area within view of the satellite.
In the United States and Europe, a GSO DBS satellite may broadcast signals within various segments of the Ku band (e.g., from 12.2 to 12.7 Gigahertz (GHz) in the U.S. and from 10.7 to 12.75 GHz in Europe). A GSO DBS satellite transponder may transmit signals at relatively high power (e.g., 100-240 Watts) per channel. The high transmission power, coupled with the geostationary orbit paths of a GSO DBS satellite, allow for the use of stationary (e.g., non-tracking) receiver antennas as small as 45 centimeters (cm) to be used in conjunction with user equipment systems. These relatively low-cost receiver antennas make GSO DBS services affordable to tens of millions of current subscribers.
However, DBS systems that employ GSO satellites suffer from several disadvantages. For example, a limited number of orbit slots in the equatorial belt are designated to DBS services, and only a handful of these orbital slots are located at the most desirable longitudes (e.g., over regions of the world that include large populations of potential users). Accordingly, a first disadvantage to GSO DBS satellite systems is that only a limited number of providers may service these areas. In addition, the equatorial orbit of the GSO satellites makes it difficult to provide adequate service in higher latitudes, because signal blocking from obstacles increases for a receiver antenna that is pointed close to the horizon. Further, GSO DBS satellite systems generally transmit signals within Ku band and higher frequencies, because of the dense orbital spacing at C band would require user antennas of an impractical size. However, signals transmitted within Ku band and higher frequencies may be significantly affected by rain attenuation. Thus, another disadvantage to GSO DBS satellite systems is that acceptable service may not be consistently achievable in areas that experience significant amounts of rain or foul weather.
An NGSO satellite has an orbit, which may have both inclination and eccentricity. Inclination causes a satellite's orbit path to pass above and below the equator, and eccentricity causes the satellite's orbital speed to slow in the vicinity of apogee. Accordingly, a satellite having an NGSO orbit path may be more easily visible users located at fairly high northern or southern latitudes. NGSO satellites, however, have apparent motion when viewed from the ground.
Because of this, NGSO systems suffer from several disadvantages. Primarily, due to the apparent motion of the NGSO satellites with respect to the Earth's surface, they are often used in systems having substantially omni-directional user antennas and receivers. Omni-directional receivers, in practice, are only used at long wavelengths, because the effective capture area is proportional to the square of the wavelength. The limited bandwidths available at long wavelengths (e.g., frequencies within the L band and S band) limit communications to narrow band signals, which are inadequate for multi-channel television transmissions. Alternatively, directional receiver antennas could be used at shorter wavelengths. However, directional receiver antennas would need to track the satellite motion. For shorter wavelength systems, the cost of the tracking antennas precludes their use for typical direct-to-home television service. Accordingly, NGSO systems have not been used for direct-to-home television service.
Many potential users within certain geographical areas have not had access to reliable, affordable, and/or practical satellite-based, digital television services. It is desirable to provide systems, apparatus, and methods to provide reliable, affordable, and practical satellite-based digital television services to geographical areas that have had limited access to such services in the past. Other desirable features and characteristics of embodiments of the inventive subject matter will become apparent from the subsequent detailed description and the appended claims, taken in conjunction with the accompanying drawings and the foregoing technical field and background.